The invention concerns at least two parts that are clamped together with at least one of the parts having a cavity receiving a moving part and having spacers in the region of the confronting clamping surfaces at the interface of the two parts.
German Patent No. 1,550,067 discloses one assembly of two clamped-together parts wherein the parts are approximately cuboid in shape and represent a valve housing and a valve baseplate of a valve housing unit. This valve housing also has a cover, and three screws extend through holes bored in the cover and in the valve housing into threaded holes in the valve baseplate. The valve housing has an axial bore that extends along the center of and parallel to the long surface of the valve housing. The valve baseplate has various inlet and outlet channels that carry liquid under pressure or not under pressure to or from a device. The flow of fluid to and from inlet and outlet channels and hence to and from the device is controlled by means of a valve spool located in and having lands fitted to the axial bore. In order to prevent the occurrence of stresses on the valve housing that might result in deformation of the housing and binding of the valve spool when the screws are tightened, the three screws are arranged so that they define the points of a triangle to achieve a stress-free three-point support. Moreover, mounted on the screws at the interface of the valve housing and the valve baseplate are spacers in the form of approximately 0.79 mm thick washers, which are intended to prevent the valve housing and the valve baseplate from touching at points outside the spacers, since otherwise the support would no longer be at only three points and stresses due to irregularities at the opposing points of the two parts would occur. In addition, a gasket is located at the interface of the valve housing and the valve baseplate to prevent loss of liquid from the inlet and outlet channels and which is compressed by the opposing sides of the valve housing and valve baseplate by the screws.
Granted, a pure three-point contact in practice would be a conceivable way of avoiding stresses in a valve housing as the screws are tightened. In fact, however, only a theoretical approximation to the ideal three-point contact has been achieved. In addition, the washers can easily be displaced when the parts are assembled and thus no longer fulfill their function. Finally, in the case of large valve housing units, the distances between the screws are so great that the clamping forces between the screws no longer suffice to compress the gasket between the valve housing and the valve baseplate sufficiently to form a liquid-tight seal.